1. Field of the Invention
The present invention relates to a numerical analysis model data generating program, a numerical analysis model data generating method, and a numerical analysis model data generating system for generating model data, which is employed in various kinds of numerical analyses, on the basis of shape data of a three-dimensional structure. More particularly, the present invention is concerned with a numerical analysis model data generating program, method, and system for generating a relatively small amount of numerical analysis model data without adversely affecting the accuracy in a numerical analysis.
2. Description of the Related Art
Along with the trend of electronic equipment, such as a notebook personal computer or a disk drive, to have a compact and lightweight design, there is a demand for a structure for properly releasing heat dissipated by the electronic equipment. The structure has to be designed by highly accurately analyzing the behavior of heat in the electronic equipment.
As a tool to assist in carrying out analysis by using a computer, various kinds of numerical analysis software have been developed. In numerical analysis of a structure, which is to be achieved by a computer, such as heat transfer analysis, mechanism analysis, or electromagnetic field analysis, three-dimensional shape data representing the structure that is an object of numerical analysis is manually segmented into numerous polyhedral elements using a predetermined mesh in order to generate a numerical analysis model. A property value representing a property of each polyhedral element is calculated. Furthermore, the property of the entire structure is calculated as a set of property values of the respective polyhedral elements.
On the other hand, software that automatically transforms the three-dimensional shape data, representing the structure that is an object of analysis, into numerical analysis model data composed of numerous polyhedral element data items has been developed.
The automatic transformation software segments the shape of a structure that is an object of analysis, defines the upper limit of the number of polyhedral elements which are to be generated (a maximum number of polyhedral elements) as a default value, and designates the numbers of meshes or segments into which the structure is segmented in each of the directions of three axes (X, Y, and Z axes). Thus, the automatic transformation software generates numerical analysis model data that has the shape of the structure, which is an object of analysis, into numerous polyhedral elements so that the number of the generated polyhedral elements does not exceed the maximum number of polyhedral elements (default value).
Herein, when the maximum number of polyhedral elements is set to a relatively small value, the number of polyhedral elements which are to be generated by segmenting the shape of the structure that is an object of analysis becomes smaller. Therefore, an analytic speed increases but an accuracy in analysis deteriorates. In contrast, when the maximum number of polyhedral elements is set to a relatively large value, the number of polyhedral elements which are to be generated by segmenting the structure that is an object of analysis becomes larger. Consequently, the accuracy in analysis improves but the analytic speed decreases.
On the other hand, in general, when the shape of a structure that is an object of analysis is segmented using a mesh, the surface of the shape thereof is inconsistent with the surface of a mesh which is to be used to segment the shape. After the shape of the structure is segmented using a mesh, the number of polyhedral elements that are objects of analysis increases. The analytic speed therefore decreases.
In efforts to cope with the above disadvantages, an analysis model generating method and system, in which three-dimensional shape data representing a structure that is an object of analysis is segmented into numerous polyhedral elements using a mesh so that an amount of numerical analysis data will be reduced, have been disclosed in Japanese Unexamined Patent Publication (Kokai) No. 10-255077 (hereinafter referred to as Patent Document No. 1).
In the analysis model generating method described in Patent Document No. 1, a calculation domain representing a structure is defined with a superficial shape. A standardized segmentation space composed of numerous polyhedral microscopic elements is defined. Among the numerous polyhedral microscopic elements, each microscopic element in which the ratio of the volume thereof to the volume of a region included in the calculation domain is smaller than a predetermined minimum filling ratio is eliminated. A set of the remaining microscopic elements is regarded as a numerical analysis model approximated to the calculation domain.
In a numerical analysis space mesh generating system described in Japanese Unexamined Patent Publication (Kokai) No. 5-307590 (hereinafter referred to as Patent Document No. 2), an operator interactively enters map information at a computer so as to carry out a two-dimensional meshing system. Furthermore, once a simple manipulation is executed and, for example, once an analysis domain is designated or the number of segments juxtaposed in a height direction or the width of each segment is designated, a three-dimensional mesh generating unit included in the computer automatically generates three-dimensional mesh data.
Furthermore, according to a three-dimensional numerical calculation mesh generating method described in Japanese Unexamined Patent Publication (Kokai) No. 5-101152 (hereinafter referred to as Patent Document No. 3), a three-dimensional numerical calculation mesh having a complex shape is accurately generated by sweeping a two-dimensional numerical calculation mesh having a basic triangle or square shape, while perfectly controlling the movements of three or four vertices by using a guide curve.
Furthermore, according to a numerical analysis automatic mesh generating method described in Japanese Unexamined Patent Publication (Kokai) No. 2001-155187 (hereinafter referred to as Patent Document No. 4), when a three-dimensional closed space including an arbitrary shape is automatically segmented, eight component points are extracted from all the component points on a plurality of interfaces constituting the closed space. Four adjoining points out of the eight component points are used to reconstruct an interface. The number of segments is set again so that the numbers of segments on opposite sides of the interface will be equal. The reconstructed interface is automatically segmented into units of a square elements. Square elements, which are contained in adjoining sections and are opposed to each other, are used to define a given hexahedral element in a space. Thus, a given hexahedral element is automatically generated in the three-dimensional closed space.
For example, according to the analysis model generating method described in Patent Document No. 1, microscopic elements whose filling ratios are smaller than the predetermined minimal filling ratios are extracted from defined polyhedral microscopic elements. The extracted microscopic elements, that is, a numerical analysis model in which data representing a microscopic projection or the like and not adversely affecting an accuracy in analysis are deleted is used to carry out numerical analysis. Consequently, while the accuracy in analysis is maintained, a high analytic speed can be assured.
However, an ordinary structure that is an object of analysis includes numerous microscopic holes, such as screw holes. Therefore, the conventional numerical analysis model data generating method described in Patent Document No. 1 causes a problem in that the holes bring about an increase in an amount of data representing the structure and eventually increase the time required for numerical analysis. For example, the results of heat transfer analysis carried out by using a numerical analysis model of a structure in which microscopic holes, such as microscopic hollows or notches, do not exist are substantially identical to the results of heat transfer analysis carried out by using a numerical analysis model of a structure having microscopic holes and having substantially the same shape. However, when heat transfer analysis is carried out by using the latter numerical analysis model, as the numerical analysis model includes microscopic holes, an amount of data, or eventually, a numerical analysis time becomes larger than that required when heat transfer analysis is carried out by using the former numerical analysis model.
On the other hand, in each of Patent Documents No. 2 to No. 4, when a numerical analysis model is generated, microscopic holes, such as microscopic hollows or notches, are not taken into consideration. Therefore, in each of these Patent Documents, a problem similar to a problem caused by Patent Document No. 1 may occur.
A conventional numerical analysis model data generating method and the underlying problems will be described later with reference to the appended drawings.